1. Field of the Invention
This invention relates to a filling machine that injects a filling into a food product and, more particularly, to a stripper for removing the food product from the filling needles.
2. Description of the Prior Art
Many food products, especially sponge cakes and cupcakes, contain a filling, such as cream, forced into the product through hollow filling needles. A filling machine continuously advances the cakes, still in their baking pans, under a filling manifold that spans the conveyor transverse to the conveying direction. The filling manifold carries one or more rows of filling-needle clusters. Drive means propel the filling manifold synchronously with the conveyor while at the same time lowering the manifold to inject the cakes with the needles and then raising the manifold to retract the needles after the cakes have been filled. The drive means then returns the filling manifold to its starting position so that the next advancing rows of cakes can be filled with cream.
Because products often tend to adhere to the filling needles as they are retracted, filling machines include structure to strip the products from the filling needles. The stripper holds the product to prevent it from rising with the needle. A common stripping arrangement uses stationary fingers that extend along the direction of conveyor travel just above the product. As the needles are retracted, any product being lifted by the withdrawing needle cluster will contact the rod, which holds the product in place and strips it from the needles. In a filling-needle cluster with four needles, each located at the corners of a square, the stripper usually has one stripper finger running through the middle of the square needle pattern and two running along opposite sides outside the square pattern.
A persistent problem is the large number of torn cakes caused by stationary stripper fingers used with continuous-advance filling machines. The moving cakes contact and rub against the stationary stripper fingers and often are torn. That is a particularly severe problem with very tender cake products such as sponge cake. Locating the stripper fingers as closely as possible to the needles ameliorates the problem because it reduces the amount of tearable cake between a finger and a retracting needle. However, a safety mechanism incorporated into many filling machines interrupts power to the machine if the needles, which are metallic, are grounded by contacting any other metal surface. If the stripper fingers are too close to the needles, a small bend in either the needle or the finger will automatically stop the machine. That safety mechanism is intended to prevent damage to the machine by stopping the machine if, for example, a baking pan becomes misaligned and a descending needle hits it. If the machine shut down every time a slightly misaligned filling needle contacted a stripper finger, however, it would significantly impede production.
Stripper fingers made of non-metallic materials would prevent inadvertent machine shutdown but would not be rigid enough. Metallic fingers can be covered with a non-metallic material, but that only temporarily solves the problem. A misaligned needle that repeatedly rubs on the non-metallic covering will eventually wear it away. The needle can then contact the metallic finger and cause machine shutdown.
In any event, the use of stationary stripper fingers, even when located as closely as possible to the filling needles, is at best only a partial solution. The stationary fingers still rub against the moving cakes and tear them. And stationary stripper fingers are for the most part impracticable if the filling needles are arranged in clusters of five instead of four, with the fifth needle in the center of the square four-needle cluster. A fifth needle provides a denser, more concentrated and therefore more suitable cream filling, but also prevents the use of the middle stripper finger. The elimination of that finger makes it virtually impossible to strip the cake without tearing.
A filling machine, built by Oakes Machine Corporation of Islip, New York, has been modified to use a stripping arrangement other than stationary stripper fingers. The Oakes filling machine is used to fill with cream cake products continuously conveyed through the machine in their baking pans. The drive means includes pneumatic cylinders, timed by a camming arrangement run by the conveyor drive, to propel the filling manifold. One end of a manifold lever arm pivotally mounts to the machine frame and the other end is attached to the filling manifold by a manifold actuating arm. The filling manifold at its ends slidably mounts to guide plates. The pneumatic cylinders reciprocate the manifold lever arm, which slides the filling manifold along the direction of movement of the conveyor. Separate pneumatic cylinders, acting through guide plate lever-arm-actuating-arm assembly, raise and lower the guide plates, and the moving filling manifold, to inject the filling needles into and retract them from the moving cakes.
The stationary stripper finger arrangement was removed from the Oakes filling machine. A pair of slide rails were attached to the machine frame. A stripper was mounted to the slide rails so that it could be reciprocated along the direction of movement of the conveyor. In an attempt to eliminate lateral relative movement between the stripper and the cake, the stripper was attached to the manifold lever arm by a stripper actuating arm. So as the manifold lever arm reciprocated the filling manifold, it reciprocated the stripper, too. The stripper itself was a stripper frame having flat stripper bars. The flat stripper bars had openings through which the filling needles passed into the cakes.
The flat stripper bars with openings, used on the modified Oakes filling machine, lessened the tearing problem encountered with the five-needle cluster. However, the arrangement used to reciprocate the stripper did not, and could not, be precisely synchronized with the moving cakes. No matter how the geometry of the manifold-lever-arm, manifold-actuating-arm, stripper-actuating-arm system was manipulated, there remained relative movement between the cakes and the stripper bars. Even though the amount of relative movement between the stripper bars and the cakes could be reduced, it could not, even under the best of circumstances, be made small enough to prevent tearing a significant number of cakes. In addition, because of the relative movement between the filling needles and the stripper bars, the openings in the stripper bars had to be elongated. The resulting slots had the effect of increasing the distance between the stripper and the filling needle, exacerbating the tearing problem.
U.S. Pat. No. 3,871,274 to Hornby shows a continuous-advance doughnut filling machine in which a stripper moves with the doughnuts. The Hornby machine has a filling head driven synchronously with a row of doughnuts moving along a conveyor. The filling head is raised and lowered as it moves with the doughnuts. A stripper plate rigidly mounts to the filling head. While the filling head is down, the filling needles are extended from the filling head through the stripper and into the doughnuts. After filling the doughnuts, the needles are retracted into the filling head, which then is raised and returned to its starting position. Because in the Hornby machine the filling needles must move relative to the filling head, it is inherently less reliable than machines having the filling needles rigidly secured to a filling head or manifold. Furthermore, reliability decreases quickly if more products are to be filled at one time, which limits the capacity of the Hornby machine. No prior art stripping apparatus is known that eliminates relative lateral movement between the stripper and the product in the simpler and more reliable filling machines having filling needles rigidly attached to the filling manifold.